A new and potentially deadly form of bird flu has claimed its first confirmed victim.

Tests revealed that a previously unknown sub-strain of the H10N8 virus killed a woman who was admitted to hospital in China with fever and pneumonia.

The woman, from Nanchang City in Jiangxi province, died nine days after becoming ill despite antibiotic and antiviral treatment.

Experts believe the strain spread from poultry and may pose the threat of a pandemic.

The dead woman had visited a live poultry market a few days prior to her illness, suggesting an incubation time of around four days - similar to that of other bird flu strains.

Reports suggest the victim was not an isolated case. At least one other person is believed to have been infected by the same strain in Jiangxi Province.

Dr Yuelong Shu, from the Chinese Centre for Disease Control and Prevention in Beijing, said: ‘A genetic analysis of the H10N8 virus shows a virus that is distinct from previously reported H10N8 viruses, having evolved some genetic characteristics that may allow it to replicate efficiently in humans.’

The strain is thought to have emerged from multiple re-assortments of genes from different bird flu viruses.

Notably, it shares genes with three other bird flu strains, H9N2, H7N9 and H5N1, the last two of which have spread to humans.

Scientists conducted tests on swab samples taken from the woman victim's windpipe.Their results, reporting the first human death associated with H10N8, appear in The Lancet medical journal.

Co-investigator Dr Qi Jin, from the Chinese Academy of Medical Sciences and Peking Union Medical College in Beijing, said: ‘Importantly, the virus had a mutation in the PB2 gene that is believed to be associated with increased virulence and adaption in mammals, and could enable the virus to become more infectious to people.’

The H10N8 strain was previously found in a water sample taken from Dongting Lake in Hunan Province in 2007.

In 2012, it was detected at a live poultry market in Guangdong Province.Co-author Dr Mingbin Liu, from Nanchang City Centre for Disease Control and Prevention warned that the threat should not be taken lightly.

‘A second case of H10N8 was identified in Jiangxi Province, China on January 26, 2014,’ said Dr Liu.

‘This is of great concern because it reveals that the H10N8 virus has continued to circulate and may cause more human infections in future.’

Dr John McCauley, director of the World Health Organisation Collaborating Centre for Influenza at the Medical Research Council National Institute for Medical Research (NIMR) in London, said: ‘This case reminds us to be aware of human infections from animal influenza viruses.

‘Previously we did not think that H7N9 infections might be so lethal.

‘More human infections by avian H10N8 viruses cannot be ruled out. H10N8 viruses are of low pathogenicity in poultry and so infection in birds is not easy to detect. Whether humans are frequently exposed and infected is also not known. ‘